I managed to find some photos that will give me a chance of explaining how a DT works. So for those that really want to know, I will give it an attempt. I will try and keep it simple for the intellectually challenged.
The first photo is an exploded view of a DT. I will give the parts some names so you can follow what I am talking about. These are not the technical names for the parts.
The first is the main disc in the middle. We will call this the Drive Plate. It fits into the main casing that you can see either side of the diagram. The crown wheel bolts to the casing and the drive plate turns with the casing. So in effect the crown wheel turns this plate.
The discs either side of the drive plate we will call the Drive Clutches, They connect via teeth to the drive plate to provide drive to the axles.
The smaller diameter tubes next to the two halves of the casing we will call the drive flanges. The axles fit inside these and the outer connects to the Drive Clutches to provide the power to the axles. I will not mention these again as any drive to the clutches is also applied to them.
Next you have the large springs. Their job is to force the clutches onto the drive plate.
The next photo shows the internals of an assembled DT.
Please note the bevel shape of the teeth. This where people are becoming confused as to the axles being locked and the diff being locked.
The only thing forcing the drive clutches to the drive plate is the pressure of the springs. You can see these in the photo. This pressure is not enough to keep them there when drive is applied. That is, the power from the drive train would force the clutches away from the plate if they were not beveled. So when the teeth on the clutches are are at either end of the teeth on the drive plate, they are “locked” to the drive plate. But they are locked there whether you are turning over the diff by hand or whether you have the throttle flat to the floor. It does not change with the amount of power provided.
You can now note that the gap between the teeth on the drive plate is larger than the size of the teeth on the clutches. So when a wheel starts to turn at a faster rate than the drive being applied, the drive clutch can move forward within the drive plate.
But you will also note that it can’t go far, so how does it unlock. We now come to the photo of the broken DT components, posted previously.
I am not interested in the breakages or the larger drive teeth. The part on the left is the drive clutch and the piece of the right is the drive plate. Now look towards the centre of these parts, you will see smaller teeth. You will note that these are shaped to allow something can slide over the top of them. Now look where the teeth are line up. The ones on the clutch are lined up with the teeth, the ones on the plate are just before the teeth. So as the clutch is turned forward by the wheel that is turning quicker through the turn, the small teeth on the clutch ride up on the ones on the plate and forces the main teeth to disengage. These teeth passing over each other is the clicking noise that you here in the diff. So as the faster wheel moves forward, the drive clutch just rides over each of the drive teeth. The spring forces the teeth to mesh again when the wheel stops turning faster.
Here is a photo of a DT with one side disengaged.
So I hope this helps explain how they work and how the axles being being locked to the drive plate does not mean that the diff is locked.
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